So for context. I come from a small town, the type where everyone moves away and then returns to raise family.
I left for uni and never returned, settling where I studied. I’ve since met a wonderful man, married and gone onto have children.
At 17 I fell in love with a lad & we were involved for about 5 years, getting together when home from uni etc but it was very one sided. I was infatuated but he’d pick me up and put me down where it suited. For a long time I thought we’d end up together properly but after the years of back and forth I ended things for my own sanity! No hard feelings, I’ve grown up and just see it as a learning experience which eventually led me to real love.
I return to the town to see my dearest friends but have never crossed paths with this ex. It’s been 20 years. Early Last year he moved back to town with new wife and they have become friends with one of my closest friends (we share lots of old friends ) Close friend is getting married and I’m a bridesmaid. Ex’s wife is invited in the hen and we have all been added to a group chat.
Last night Exs wife messaged me privately. Said she “knew who I was” and “what I meant to Ex” and wanted it put out there so there was no weirdness. 
I simply replied “Hi, nice to meet you, but I’m not quite sure what you mean” because I had no idea of her angle.
She went onto say the Ex had told her how I was once the love of his life and the one that got away.
I haven’t replied because I have no idea how to. Do I reply flippantly, no problem type thing or should I explain what it was in my eyes??
I kinda want to brush over it because it’s weird to hear this new take on my history!!!